Protecting effects of cephalosporins (cefazolin, cefotaxime, cefoperazone and cefsulodin), cepha. mycin (cefmetazole) and oxacephem (latamoxef) against, xperimental mice mixed infection with E. coli and P. aeruginosa were investigated and the results were taken as follows:
1) ED₅₀ values of all antibiotics to the mixed infection were larger than to the single infection with the equal dose. Protecting effects of all antibiotics fell.
To the single infection with E. coli in a dose above MLD, small ED₅₀ followed cefotaxime, latamoxef, cefoperazone, cefazolin, cefmetazole and cefsulodin in order and with P. aeruginosa, followed cefsulodin, latamoxef and cefoperazone.
To the mixed infection, latamoxef was the most effective among the test antibiotics and the efficacy of cefsulodin and cefoperazone followed that of latamoxef in that order in small dose.
2) From the heart blood of each dead mouse after antibiotics administration, cefsulodin administered groups were cultivated E. coli, whereas on other antibiotics, large dose administered groups were cultivated P. aeruginosa and small dose administered groups, .vere cultivated P. aeruginosa and E. coli.
3) Serum levels of normal mice were cefazolin, latamoxef, cefmetazole, cefotaxime, cefoperasone and cefsulodin in order of height. But at the mixed infectious mice latamoxef was higher serum level than cefazolin.

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Fourteen patients were administered fosfomycin in combination with dibekacin to investigate the usefulness of this combined therapy against complicated urinary tract infections. The former was given in a single dose of 2g twice a day by intravenous drip infusion, while the latter a single dose of 50 mg twice a day intramuscularly, both for 5 days. The clinical and bacteriological efficacy, and side effects were then evaluated and the in vitro combined effect of the drugs on 6 strains of clinical isolates was also found by chequer board method.
1. Overall, the combined therapy of fosfomycin and dibekacin was clinically effective in 78.6% of 14 patients with complicated urinary tract infections.
2. Twelve (71%) of the 17 strains of 8 bacterial species were eradicated by the therapy.
3. Combined efficacy by chequer board method was found against Escherichia coli, Pseudomonas aeruginosa, Pseudomonas cepacia, Pseudomonas morganii, Pseudomonas rettgeri and Serratia marcescens.
4. There were no subjective or objective clinical side effects. No appreciable change was seen in the results of clinical and laboratory data on peripheral blood and renal function tests, nor was there any change in the results of hepatic function tests except slight and transient rises in the serum GOT and GPT levels in several cases.
5. From the above-mentioned results, we think that combined therapy with fosfomycin and dibekacin is useful in the treatment of complicated urinary tract infections.

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Single 75mg doses of netilmicin, were administered once intramuscularly to 3 healthy volunteersand 9 hospitalized patients suffering from various degrees of renal disfunction with creatinine clearance(C_cr) from 1.6 to 104ml/min, and netilmicin levels in serum and urine were determined by bioassay, and pharmacokinetic analysis were performed by the one component open model.
The maximum serum level of netilmicin(C_max) obtained from the mean serum level in the volunteers was 4.6μg/ml, the half life in serum(t_1/2) was 1.77 hrs, body serum clearance(CL_B) was 81.4ml/min, and renal clearance (CL_R) was 75.3ml/min.
The MICs of netilmicin tested clinically isolated pathogenic bacteria in Japan and the duration of the effective levels of netilmicin in serum, which was calculated from the simulated netilmicin serum levels using the pharmacokinetic parameters obtained, were compared. As the result, it was found that the following dosage regimen was established: 75 mg of netilmicin is administered every 12 hrs for the infectious disease with S. aureus, and every 8 to 12 hrs for the infectious disease with the gram negative bacilli. Repeated administration of 75 mg of netilmicin in every 8 hrs would not induce any adverse reactions.
As renal function decreased, CL_R was decreased. The mean CL_R and t_1/2 in 3 patients with a creatinine clearance below 10ml/min. were 2.0-3.0ml/min. and 22.9hrs. respectively. The relationship between the elimination rate constant(K_el) and C_cr was expressed as K_el=0.0043 C_cr-0.0006. The calculated nomogram of netilmicin for the initial dose and maintenance dose in patients with various degrees of renal insufficiency, when netilmicin is administered every 8 hrs and 12 hrs, was obtained.
Serum levels in 6 subject, and urinary levels in 3 subjects were determined by radioimmunoassays (RIA) as well as by bioassays, and the both were well correlated, the correlation coefficients being 0.943 and 0.990, respectively. It may suggested that RIA method is considered to be a rapid assay method to determine the serum level of netilmicin.

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Solitary lung abscess was produced by inoculating intrabronchially both Staphylococcus aureus and Klebsiella pneumoniae mixed with Freund's incomplete adjuvant through a tube inserted perorally to one lung of a rabbit which had been sensitized with mixture of killed Staphylococcus aureus and Freund's incomplete adjuvant. After the inoculation, macroscopic and histologicalfindings of lung abscess and viable cell counts in the various tissues of the lung were investigated at several times. The results were compared with those of lung abscess due to Staphylococcus aureus alone. The results obtained were as follows.
1): In rabbits inoculated with 10⁹ CFU of Staphylococcus aureus and 10⁶ CFU of Klebsiella pmeumooniae (group I), lung abscess were produced in 57%, of them. In rabbits inoculated with 10⁹ CFU of Staphylococcus aureus and 10³ CFU of Klebsiella pneftmoniae (group II), abscess formation was observed in 64%. Either of these incidences of abscess formation in rabbits with mixed infection was higher then that in rabbits with infection due to Staphylococcus aureus alone.
2) Lesions due to Staphylococcus aureus and Klebsiella pneumoniere were larger than those due to Staphylococcus aureus alone.
3) In both group I and II, viable cells of Staphylococcus aurcus and Klebsiella pnelemoniae itissues were counted in the order of decreasing number; most in pus>abscess wall>least in surrounding tissues. The numerical order of viable cells in the above was the same as that of viable cells in the lung abscess due to Staphylococcus dierefes alone.
4) In group I viable cells of Klebsiella pneumoniae in the lesion was predominant in number, while Staphylococcus aureus was predominant in group II.
5) As time passed by, viable cells in the lesion decreased gradually and the bacteria which were predominant in one week after inoculation survived longer than the other in both group. In group I, the tendency was observed that large number of Klebsiella pneitmoniae survived longer in the abscess wall.

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Distribution of aminoglycoside antibiotics in the renal cells was examined at the subcellular level using tritium labeled kanamycin and dibekacin. Inhibition of protein biosynthesis within the renal cortex was suggested, as the result, by these antibiotic agents, and the result of the examination of protein biosynthesis is also reported:
1. Aminoglycoside antibiotics were incorporated in the renal cortex in rats, and accumulated there.
2. They were distributed in high concentration in the rough microsome fraction in the renal cortex, particularly in the ribosome, and the accumulation was notable even after 24 hours of the administration.
3. Similar combination of aminoglycoside antibiotics and ribosome was observed in in vitro experiment, and they combined with ribosome in the liver and kidney firmly in the same degree, and no organ specificity was observed.
4. Ratio of RNA in the submicrosome fractions and aminoglycoside antibiotics was a constant in any fractions, suggesting that the antibiotics combine with RNA rather than protein.
5. In pretreated rats with aminoglycoside antibiotics, incorporation of ³H-leucine was suppressed, and the suppression was antibiotics concentration dependent.
6. Inhibition of ³H-leucine incorporation was not shown in the liver of kanamycin administered rats, and concentration difference of kanamycin in various organs was notable.
7. In vitro experiments of protein biosynthesis in the renal cortex ribosome in rats showed that effect of protein biosynthesis inhibition was nearly proportional to the renal toxicity of antibiotics, and the degree of inhibition was in the order of dibekacin, gentamicin, netilmicin and kanamycin.

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Renal toxicity of aminoglycoside antibiotic agents, particularly gentamicin and netilmicin, was examined for the comparison. The toxic effect, in vitro, of these antibiotic agents on the ribosomal function and lysosomal membrane was examined in isolated ribosome from normal rats, and the following results were observed.
1. Gentamicin and netilmicin exerted effects on ribosomal functions, and incorporation of ³H-leucine was suppressed.
2. The suppression was dependent on the concentration of antibiotic agents, and, particularly, high gentamicin concentration inhibited more than 90% of the ³H-leucine incorporation.
3. Comparing the inhibitory action of gentamicin and netilmicin, the former showed 3 times greater inhibition than the latter.
4. Denaturation of lysosomal granules was examined by means of light-scattering property to see the effect on the lysosomal membrane, and the effect of gentamicin was slightly stronger than netilmicin.
5. Lysosomal membrane was denatured immediately after the addition of the both antibiotic agents, and isolation of protein from the lysosomal granules was stimulated, and gentamicin exerted 2-3 times larger effects than netilmicin.
6. Damage of lysosomal membrane was examined using acid phosphatase activity and β-N-acetylglucosaminidase activity as indices, and the both antibiotic agents exerted concentration dependent effect, and available activity of lysosome was increased but soluble activity did not show significant change.
7. Effect of gentamicin on the denaturation of membrane of lysosomal granules (change of available activity) was 2-3 times larger than that of netilmicin.

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In vitro synergistic effects of cephalexin and mecillinam against Escherichia coli, Klebsiclla pneunzoniae, Enterobacter spp. Serratia marcescens and Proteus spp. were demonstrated by the chequerboard titration and fixed combination method, and thein vito effect of these two antibiotics and their mechanism of action were also discussed.
The growth curve after the exposure of cephalexin and mecillinam at the concentrations at which these antibiotics had no effects when given alone showed a decrease of the turbidity and the presence of a bactericidal effect. In experimental infection in mice, the combination of both drugs showed a synergistic effect and excellent therapeutic effect. The blood concentration ratio of cephalexin to mecillinam was coincident with the concentration ratio of these antibiotics at which the synergistic effect was observed in vitro.Phase-contrast and scanning electron micrographs of bacterial cells exposed to the combination of cephalexin and mecillinam showed somewhat elongated bacteria and formation of spindle cells with swelling in the central part; cephalexin caused formation of filamentous cells, while mecillinam caused formation of ovoid cells. Cephalexin showed an affinity for PBP-1 a and 3, and mecillinam showed an affinity for PBP-2. When these antibiotics were used concurrently, they exerted an additive effect to increase the affinity for PBPs. The lytic activity was increased much more after the combination of two antibiotics than after a single exposure.

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Latamoxef (6059-S), a novel oxacephem, has a stronger antibacterial activity against various gramnegative organisms than commercially available β-lactam antibiotics. The antibacterial action was investigated against Pseudomonas aeruginosa KM 338, Serratia marcescens IFO 12648, and Escherichia coli, and was compared with that of cefazolin and benzylpenicillin.
The minimum inhibitory concentrations (MICs) for these organisms were 12.5, 0.2 and 0.39μg/ml, respectively. The addition of subinhibitory concentration (1/2 MIC) of ethylenediaminetetraacetic acid (EDTA), which damages permeability barrier of the outer membrane, caused no change in the MICs of latamoxef for P. aeruginosa and S. marcescens, whereas marked reduction in the MICs of cefazolin and benzylpenicillin was observed in the presence of EDTA. Latamoxef was stable to β-lactamase activities from these organisms whereas cefazolin was hydrolyzed rapidly by the enzymes. The crosslinking reaction of peptidoglycan synthesis catalyzed by the ether-treated cells from these orgaisms was inhibited by markedly lower concentration of latamoxef than that of cefazolin and benzylpenicillin.
These results suggest that the potent activity of latamoxef against P. aeruginosa and S. marcescensis attributed to its high permeability of the outer membrane, the stability to hydrolysis by β-lactamase, and the high sensitivity to the target enzymes (transpeptidase).

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